Sheet feeding apparatus and image forming apparatus

ABSTRACT

The present invention provides a sheet feeding apparatus and an image forming apparatus which can suppress generation of sheet skew feeding by a simple configuration and a pair of side edge regulating portions  30   r  and  30   l  is provided opposite each other in a sheet storage portion in order to regulate positions of side edges in a width direction orthogonal to a sheet feeding direction of the stored sheet S. At least one of the side regulating plates  30   r  and  30   l  can be moved in the width direction, and abutting portions  301   r  and  301   l  are provided opposite each other on inner wall surfaces of the side regulating plates  30   r  and  30   l  to abut on side edges of the sheet S.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet feeding apparatus and an imageforming apparatus, particularly to a configuration of a side edgeregulating portion that regulates a side edge position of a sheet storedin a sheet storage portion detachably attached to an apparatus mainbody.

2. Description of the Related Art

Currently, in an image forming apparatus such as a copying machine, aprinter, and a facsimile machine, one in which a sheet is fed from asheet feeding apparatus to an image forming portion to form an imagebecomes widespread. In the sheet feeding apparatus, generally a sheetcassette which is the sheet storage portion is detachably attached to anapparatus main body, and the sheet stored in the sheet cassette isautomatically fed to the image forming portion.

In some sheet cassette used in the sheet feeding apparatus, for example,a sheet stacking portion which is pressed against a sheet feeding rollerwhile stacking the sheet thereon is provided in a lifting and loweringmanner. In the sheet cassette provided with the sheet stacking portion,a tailing end regulating member is slidably provided. The tailing endregulating member regulates a position of a tailing end in a sheetfeeding direction (hereinafter referred to as a tailing end) of thesheet which is stacked on and stored in the sheet stacking portion suchthat sheets having different sizes can be stored in the sheet cassette.A pair of side edge regulating portions is slidably provided to regulatea side edge position in a direction (hereinafter referred to as a widthdirection) orthogonal to the sheet feeding direction in delivering thesheet.

In the sheet cassette, the tailing end of the sheet is regulated by thetailing end regulating member while the side edges of the sheet isregulated by the pair of side edge regulating portions, whereby aleading end position of the sheet is always regulated in a predeterminedposition. Therefore, when the sheet cassette is accommodated in theapparatus main body, the sheet can stably be fed irrespective of thesheet size.

Since the side edge regulating portion is configured to be slidaccording to the sheet size, an attachment allowance exists due to theconfiguration, and the side edge regulating portion may be inclined withrespect to the sheet feeding direction. Even if the side edge regulatingportion is not inclined, slight irregularity may exist in the side edgeregulating portion due to a manufacturing tolerance.

When the side edge regulating portion is inclined, or when the slightirregularity exists in the side edge regulating portion, the sheet maybe inclined with respect to the sheet feeding direction when the sideedge regulating portion abuts on the side edge of the sheet after thesheet is stored in the sheet cassette. The phenomenon will be describedwith reference to FIGS. 12A and 12B. Side regulating plates 30 r and 30l which are the side edge regulating portions has the attachmentallowances because the side regulating plates 30 r and 30 l areconfigured to be able to be moved in the width direction. In the sideregulating plates 30 r and 30 l, the slight irregularity exists on aregulating surface facing a sheet S when viewed in the whole area in thesheet feeding direction.

Therefore, as illustrated in FIG. 12A, the side regulating plates 30 rand 30 l have the same inclination of an angle θ with respect to thesheet feeding direction. The case, in which the sheet S is positioned bythe side regulating plates 30 r and 30 l having the inclinations of theangles θ with respect to the sheet feeding direction and lengths X inthe sheet feeding direction after a leading end of the sheet S abuts onan abutting surface 3 f to stack the sheet S based on the leading end ofthe sheet S, will be described below.

Conventionally, the lengths X in the sheet feeding direction of the sideregulating plates 30 r and 30 l is increased as much as possible (forexample, 60 mm or more) because the sheet S is regulated in a distanceas long as possible. However, when the side regulating plates 30 r and30 l are inclined with respect to the sheet feeding direction, the sheetS may be inclined by an attaching state or component accuracy ifregulated in the long distance.

For example, as illustrated in FIG. 12A, when the side regulating plates30 r and 30 l are inclined by the angle θ with respect to the sheetfeeding direction, abutting points R1 and L1 between the side regulatingplates 30 r and 30 l and the sheet S are shifted by X cos θ in the sheetfeeding direction. The inclination θ generated by the attachmentallowances of the side regulating plates 30 r and 30 l depends on theconfiguration. However, generally the inclination θ satisfies θ<0.5°.Therefore, approximation of X cos θ≈X holds with no incident. Assumingthat Y is a length in the width direction of the sheet S, a distanceconnecting the abutting points R1 and L1 between the side regulatingplates 30 r and 30 l and the sheet S by a straight line can be expressedby √(X2+Y2).

At this point, the sheet S is subjected to forces F1 at the abuttingpoints R1 and L1 between the sheet S and the side regulating plates 30 rand 30 l, when the sheet S is positioned such that the side regulatingplates 30 r and 30 l are moved to abut on the sheet S. When the sheet Sis subjected to the forces F1 at the abutting points R1 and L1, theabutting points R1 and L1 become power points and also become fulcrumsabout which the sheet is rotated. Therefore, rotation moment isgenerated clockwise in the sheet S as illustrated in FIG. 12B, magnitudeof the rotation moment is proportional to X cos θ and the forces F1acting on the abutting points.

As the lengths X of the side regulating plates 30 r and 30 l areincreased, and as the forces F1 of the side regulating plates 30 r and30 l are increased, the rotation moment generated in the sheet S isincreased to enhance a possibility that the sheet S is rotated asillustrated in FIG. 12B. The inclination of the sheet S cannotcompletely be corrected even if the tailing end regulating plate 31abuts on the tailing end of the sheet S. Therefore, the positioning ofthe sheet S is completed while the sheet S may be inclined with respectto the sheet feeding direction. In such cases, skew feeding of the sheetS is generated when the sheet S is fed by a sheet feeding roller 3 c. Asdescribed above, when the sheet is inclined while the settings of theside regulating plates 30 r and 30 l are completed, because the sheet isfed while inclined, the skew feeding of the sheet is generated, whichpossibly leads to degradation of printing accuracy.

On the other hand, when the side edge regulating portion having theinclination abuts on the sheet, the sheet may not be aligned with theside edge regulating portion. In such cases, a gap is generated betweenthe side edge regulating portion and the side edge of the sheet. At thispoint, when a force rotating the sheet acts on the sheet due to anunbalance between right and left pressures of the sheet feeding roller,because the sheet is rotated until the side edge abuts on the side edgeregulating portion, possibly the skew feeding is generated depending onthe position of the gap.

The case, in which the sheet S positioned by the side regulating plates30 r and 30 l having the inclinations of the angles θ with respect tothe sheet feeding direction is fed by the sheet feeding roller 3 c, willbe described below with reference to FIG. 13. FIG. illustrates a stateimmediately after the leading end of the sheet S is fed by the sheetfeeding roller 3 c. In feeding the sheet S, the sheet S is regulated atthe two abutting points R1 and L1 of the side regulating plates 30 r and30 l. The sheet S may be subjected to a force F2 illustrated in FIG. 13depending on a difference between right and left diameters of the sheetfeeding roller 3 c, a pressure balance between the right and leftdiameters, and alignment of the sheet feeding roller 3 c with respect tothe sheet feeding direction. The clockwise (CW) rotation moment isgenerated in the sheet S by the force F2, and the sheet S is rotateduntil the gaps between the side edges and the side regulating plates 30r and 30 l are filled.

At this point, because the gap can be expressed by √(X2+Y2)−Y, adisplacement amount is increased with increasing lengths X of the sideregulating plates 30 r and 30 l, whereby a skew feeding amount isincreased. When the side regulating plates 30 r and 30 l are inclinedwith respect to the sheet feeding direction, it is disadvantageouslyfound that the skew feeding amount generated in the sheet S inpositioning or feeding the sheet S is increased with increasing lengthsX of the side regulating plates 30 r and 30 l.

There is discussed a sheet feeding apparatus including an angleadjusting portion that adjusts an angle of the side edge regulatingportion with respect to the sheet feeding direction (for example, seeJapanese Patent Laid-Open No. 2005-263458). When the sheet feedingapparatus includes the angle adjusting portion, a service engineer or auser can simply adjust the sheet feeding apparatus to the desired skewfeeding accuracy according to a variation in manufacturing tolerance ofthe sheet feeding apparatus.

Recently, the laser beam printer and the copying machine is widely usedin not only offices but also home with low cost and miniaturization, anda demand for improvement of usability is increased. In the conventionalsheet feeding apparatus and image forming apparatus in which the angleof the side edge regulating portion is adjusted, it takes asignificantly long time for not the service person but the individualuser to see a sample to adjust the angle of the side edge regulatingportion. As a result, productivity of the sheet feeding apparatus isdegraded to decrease the usability. That is, it takes a long time toadjust the angle of the side edge regulating portion in order to preventthe skew feeding in positioning or feeding the sheet. An angle adjustingmechanism is also required to complicate a structure.

The present invention provides a sheet feeding apparatus and an imageforming apparatus which can suppress the generation of the sheet skewfeeding by a simple configuration.

SUMMARY OF THE INVENTION

According to an aspect of the invention, a sheet feeding apparatuscomprising: a sheet storage portion which stores sheets; a sheet feedingroller which feeds the sheet stored in the sheet storage portion; a pairof side edge regulating portions which is provided opposite each otherin the sheet storage portion so as to regulate positions of side edgesin a width direction orthogonal to a sheet feeding direction of thestored sheet, and at least one of the pair of side edge regulatingportions can be moved in the width direction; and projection portionsprovided opposite each other on inner wall surfaces of the side edgeregulating portions so as to abut on the side edges of the sheet,respectively.

According to the invention, the projection portion which abuts on eachside edge of the sheet is provided on the inner wall surface of the pairof side edge regulating portions, which allows the generation of thesheet skew feeding to be suppressed by the simple configuration.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic configuration of a printer which is anexample of an image forming apparatus provided with a sheet feedingapparatus according to a first embodiment of the invention;

FIG. 2 is a perspective view of the sheet feeding apparatus;

FIG. 3 is a perspective view illustrating a movable portion of a sideregulating plate provided in the sheet feeding apparatus;

FIG. 4A illustrates a configuration of the side regulating plate (leftmember); FIG. 4B illustrates a configuration of the side regulatingplate (right member); FIG. 4C is a plan view illustrating theconfigurations of the side regulating plates;

FIG. 5A illustrates a sheet positioning operation performed by the sideregulating plates; FIG. 5B illustrates the sheet positioning operationperformed by the side regulating plates;

FIG. 6 illustrates a state immediately after a sheet positioned by theside regulating plates is fed by a sheet feeding roller;

FIG. 7 is a table illustrating a determination result of a length of anabutting portion of the side regulating plate to a tolerance of a skewfeeding amount;

FIG. 8A illustrates a side regulating plate (right member) provided in asheet tray of a sheet feeding apparatus according to a second embodimentof the invention; FIG. 8B illustrates a side regulating plate (leftmember) provided in the sheet tray of the sheet feeding apparatus of thesecond embodiment; FIG. 8C is a plan view illustrating the sideregulating plates provided in the sheet tray of the sheet feedingapparatus of the second embodiment;

FIG. 9A illustrates a sheet positioning operation performed by the sideregulating plates; FIG. 9B illustrates the sheet positioning operationperformed by the side regulating plates;

FIG. 10A illustrates a configuration of a movable portion of a sideregulating plate provided in a sheet tray of a sheet feeding apparatusaccording to a third embodiment of the invention; FIG. 10B is anenlarged view illustrating the configuration of the movable portion ofthe side regulating plate provided in the sheet tray of the sheetfeeding apparatus of the third embodiment;

FIG. 11 is a perspective view of the side regulating plate;

FIG. 12A illustrates a sheet positioning operation performed byconventional side regulating plates; FIG. 12B illustrates the sheetpositioning operation performed by conventional side regulating plates;and

FIG. 13 illustrates a state immediately after a sheet positioned by theconventional side regulating plates is fed by a sheet feeding roller.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments of the invention will be described indetail with reference to the drawings. FIG. 1 illustrates a schematicconfiguration of a printer which is an example of an image formingapparatus provided with a sheet feeding apparatus according to a firstembodiment of the invention. In a printer 50 of FIG. 1, an image formingportion 52 is provided in a printer main body 51 which is an apparatusmain body, the image forming portion 52 performs image formation by anelectrophotographic system, and a sheet feeding apparatus 3 feeds asheet S to the image forming portion 52.

The image forming portion 52 includes a laser exposure device 1, aphotosensitive drum 207 which forms a toner image, and a transfer roller4 which transfers the toner image formed in the photosensitive drum 207to the sheet S. A process cartridge B includes the photosensitive drum207, a charging roller (not illustrated), and a development portion (notillustrated). The process cartridge B is detachably attached to theprinter main body 51.

The sheet feeding apparatus 3 includes a sheet feeding roller 3 c, asheet tray 3 a which is a sheet storage portion, and a lift-up plate 3b. The lift-up plate 3 b is provided in the sheet tray 3 a in a liftingand lowering manner, and presses the sheet S stored in the sheet tray 3a against the sheet feeding roller 3 c. A separation pad 3 d whichpresses the sheet feeding roller 3 c is provided on a downstream side ina sheet feeding direction of the sheet tray 3 a. In the sheet feedingapparatus 3, during the image formation, the sheet S is delivered fromthe sheet tray 3 a by the sheet feeding roller 3 c, and the sheet S isseparated one by one by the separation pad 3 d which presses the sheetfeeding roller 3 c.

An image forming operation in the printer 50 having the above-describedconfiguration will be described below. When the image forming operationis started, the photosensitive drum 207, which is rotated in an arrowdirection while a charging treatment is performed to a surface of thephotosensitive drum 207, is irradiated with a laser beam L emitted fromthe laser exposure device 1 according to an image signal. A latent imageis formed on the photosensitive drum 207 by the laser irradiationaccording to the image signal. The latent image on the photosensitivedrum 207 is developed and visualized as a toner imager by toner suppliedby the development portion.

The lift-up plate 3 b is lifted in parallel with the toner image formingoperation, the sheet S set in the sheet tray 2 a is delivered byfriction with the sheet feeding roller 3 c, and the sheet S is separatedone by one and substantially vertically fed by the separation pad 3 d.Then the sheet S is conveyed to a transfer portion by a pair ofconveying rollers 3 e.

In the transfer portion, a voltage having an opposite polarity to thetoner image formed on the photosensitive drum 207 is applied to thetransfer roller 4, thereby transferring the visualized toner image onthe photosensitive drum 207 to the sheet S. Then the sheet S to whichthe toner image is transferred is conveyed to a fixing unit 5, which isdisposed in an upper portion of the printer main body, by a conveyanceguide 3 f. The fixing unit 5 includes a driving roller 5 a and a heaterunit 5 c in which a heater 5 b is incorporated. In the fixing unit 5,the transferred toner image is fixed by applying heat and pressure tothe passing sheet S. Then the sheet S to which the toner image is fixedis conveyed by a pair of discharge rollers 3 g and discharged to adischarge portion 6 provided on an upper surface of the printer mainbody 51.

As illustrated in FIG. 2, a tailing end regulating plate 31 is providedin the sheet tray 3 a to regulate a tailing end which is an upstreamside edge in the sheet feeding direction on the lift-up plate 3 b. Thetailing end regulating plate 31 can slidably be moved along the sheetfeeding direction and disposed at a position corresponding to a sheetsize. The tailing end regulating plate 31 is pressed against the tailingend of the sheet S, and a leading end of the sheet S abuts on anabutting surface 3 f, thereby determining the position of the sheet S inthe sheet feeding direction based on the leading end of the sheet S.

The sheet tray 3 a includes a pair of side regulating plates 30 r and 30l. The side regulating plates 30 r and 30 l abut on both side edges in awidth direction orthogonal to the sheet feeding direction of the sheet Sstacked on the lift-up plate 3 b and regulate side edge positions of thesheet S. The side regulating plates 30 r and 30 l are supported by aside regulating plate guide 32 while being slidable in the widthdirection. In not only standard-size sheets such as an A4 size and aletter size but also nonstandard-size sheets such as a postcard and anenvelope, the side edge positions of the sheet S can be aligned by theside regulating plates 30 r and 30 l which are a side edge regulatingportion.

The sheet feeding apparatus of the first embodiment performs a centerregistration type sheet feed. Therefore, as illustrated in FIG. 3, theside regulating plates 30 r and 30 l include rack members 7 r and 7 lwhich are slid in conjunction with each other, and the rack members 7 rand 7 l engage with a pinion 8 which is journaled at a bottom of theside regulating plate guide 32.

When one of the side regulating plates 30 r and 30 l is moved inregulating the side edge positions of the sheet S, the rack members 7 rand 7 l are guided by a lateral guide groove 32 a formed in the widthdirection of the side regulating plate guide 32, thereby also moving theother side regulating plate in conjunction with one of the sideregulating plates 30 r and 30 l. The rack members 7 r and 7 l areretained at the moved positions by a frictional force with the sideregulating plate guide 32.

FIG. 4 illustrates configurations of the side regulating plates 30 r and30 l of the first embodiment. As illustrated in FIGS. 4A and 4B, theside regulating plates 30 r and 30 l include abutting portions 301 r and301 l on inner wall surfaces thereof, respectively. The abuttingportions 301 r and 301 l are projection portions whose lengths X′ in thesheet feeding direction are short (for example, 5 mm or less). When theabutting portions 301 r and 301 l are provided one by one, the side edgeof the sheet S and each of the abutting portions 301 r and 301 l becomea state of a substantial point contact.

As described above, the rotation moment applied to the sheet S isproportional to the length X in the sheet feeding direction of each ofthe side regulating plates 30 r and 30 l. Therefore, when the side edgeof the sheet S and each of the abutting portions 301 r and 301 l becomethe state of the substantial point contact like the first embodiment,because the rotation moment applied to the sheet S is decreased even ifthe side regulating plates 31 r and 31 l are inclined, the sheet S ishardly influenced by the inclinations of the side regulating plates 30 rand 30 l.

As illustrated in FIG. 4, the pair of abutting portions 301 r and 301 lis provided across the sheet S from each other. When the lengths X′ inthe sheet feeding direction of the abutting portions 301 r and 301 l areshort (for example, 5 mm or less), directions of forces acting on thesheet S by the abutting portions 301 r and 301 l become thesubstantially same straight line orthogonal to the sheet feedingdirection. As a result, deviations in the sheet feeding direction ofabutting points between the abutting portions 301 r and 301 l and thesheet S are eliminated, and the generation of the rotation moment by thedeviations in the sheet feeding direction at abutting points L1 and R1can be prevented when the abutting portions 301 r and 301 l abut on thesheet S.

A positioning operation of the sheet S, which is performed by the sideregulating plates 30 r and 30 l having the above-describedconfiguration, will be described below with reference to FIG. 5. FIG. 5Aillustrates a state before the sheet S is positioned, and FIG. 5Billustrates a state after the sheet S is positioned.

When the side regulating plates 31 r and 31 l are moved from thepositions illustrated in FIG. 5A, the side edges of the sheet S and theabutting portions 301 r and 301 l become the state of the substantialpoint contact as illustrated in FIG. 5A. Irrespective of an inclinationθ with respect to the sheet feeding direction, the abutting portions 301r and 301 l abut on the sheet S at the substantially same position inthe sheet feeding direction, namely, with no deviation in the sheetfeeding direction. As illustrated in FIG. 5B, the sheet S does notrotate, because the rotation moment is not generated in the sheet S evenif the sheet S is subjected to forces F4 from the abutting portions 301r and 301 l. Therefore, the sheet S is hardly inclined when the sheet Sis positioned.

FIG. 6 illustrates a state immediately after the leading end of thesheet S is fed by the sheet feeding roller 3 c. The sheet S is subjectedto forces F5 at the abutting portions 301 r and 301 l depending on adifference between right and left diameters of the sheet feeding roller3 c, a pressure balance between the right and left diameters, andalignment of the sheet feeding roller 3 c with respect to the sheetfeeding direction. On the other hand, in the first embodiment, theabutting portions 301 r and 301 l of the side regulating plates 31 r and31 l abut on the side edges of the sheet S at the same position in thesheet feeding direction to regulate an attitude of the sheet S.Therefore, a gap is eliminated unlike the conventional art, but thesheet S does not rotate. Consequently, in the first embodiment, the skewfeeding of the sheet S is not generated during the sheet feed.

In the first embodiment, until the leading end of the sheet S reachesthe pair of conveying rollers 3 e since the sheet S is fed by the sheetfeeding roller 3 c, the abutting portions 301 r and 301 l of the sideregulating plates 31 r and 31 l are set to positions at which theabutting portions 301 r and 301 l can abut on the side edges of thesheet S. Plural pairs of conveying rollers 3 e constituting the sheetconveying portion are provided in the width direction. In the firstembodiment, two pairs of conveying rollers 3 e are provided, and the twopairs of conveying rollers 3 e convey the sheet S while nipping thesheet S, thereby stabilizing the attitude of the sheet S. Therefore, thesheet S is regulated by the abutting portions 301 r and 301 l such thatthe attitude of the sheet S does not change until the leading end of thesheet S reaches the pairs of conveying rollers 3 e, so that the skewfeeding of the sheet S can be prevented from the feed to the conveyance.

In the first embodiment, the lengths X′ in the sheet feeding directionof the abutting portions 301 r and 301 l of the side regulating plates31 r and 31 l are set to 5 mm or less. However, there is no limitationto the lengths X′ in the sheet feeding direction of the abuttingportions 301 r and 301 l. FIG. 7 illustrates a determination result ofthe lengths X′ of the abutting portions 301 r and 301 l of the sideregulating plates 31 r and 31 l to a tolerance of a skew feeding amount.In the first embodiment, the tolerance of the skew feeding amount is setto 0.5% of a long side (sheet feeding direction) of the sheet S, and 150letter-size (215.9 mm×279.4 mm) sheets Shaving a basis weight of 75 g/m²are stacked. The skew feeding amount is determined when the 150 sheets Sare positioned.

As illustrated in FIG. 7, the skew feeding amount falls within thetolerance in a range of X′ (lengths of the abutting portions 301 r and301 l of the side regulating plates 31 r and 31 l) 30 (mm). Therefore,the effect of the first embodiment is exerted when the length X′ of eachof the abutting portions 301 r and 301 l of the side regulating plates31 r and 31 l is set to the range of X′≦30 (mm). Usually the sideregulating plates 31 r and 31 l are molded by a synthetic resin. In theside regulating plates 31 r and 31 l, a thickness of at least 0.5 mm isrequired to cause the synthetic resin to flow to details of a mold.Accordingly, the length X′ of each of the abutting portions 301 r and301 l of the side regulating plates 31 r and 31 l is set to the range of0.5 (mm)≦X′≦30 (mm).

As described above, in the first embodiment, the abutting portions 301 rand 301 l of the side regulating plates 31 r and 31 l abut on the sideedges of the sheet S in the state of the substantial point contact andthe state in which the deviation in the sheet feeding direction iseliminated. Therefore, when the lengths X′ in the sheet feedingdirection of the abutting portions 301 r and 301 l are short (forexample, 5 mm or less), directions of forces acting on the sheet S bythe abutting portions 301 r and 301 l become the substantially samestraight line orthogonal to the sheet feeding direction. As a result,the generation of the sheet skew feeding can be suppressed by the simpleconfiguration.

When the lengths X′ in the sheet feeding direction of the abuttingportions 301 r and 301 l are 5 mm or more, sometimes the directions ofthe forces acting on the sheet do not become the substantially samestraight. Even in this case, although accuracy is slightly degraded, thegeneration of the skew feeding of the sheet can be suppressed betterthan ever before. In the configurations of the side regulating plates 31r and 31 l of the first embodiment, because the regulating portion whichregulates the sheet S is restricted compared with the conventionalconfigurations, the size is easily managed on the production.

A second embodiment of the invention will be described below. FIGS. 8Ato 8C illustrate a side regulating plate provided in a sheet tray of asheet feeding apparatus according to a second embodiment of theinvention. In FIGS. 8A to 8C, the same or equivalent component isdesignated by the same numeral as that of FIGS. 4A to 4C.

In FIGS. 8A and 8B, the numerals 32 r and 32 l designate side regulatingplates. Similarly to the side regulating plates 31 r and 31 l of thefirst embodiment, the side regulating plates 32 r and 32 l includeabutting portions 302 r and 302 l having lengths δ (≦30 mm) in the sheetfeeding direction, respectively. As illustrated in FIG. 8, the sideregulating plates 32 r and 32 l include regulating portions 322 r and322 l, respectively. The regulating portions 322 r and 322 l arecontinuously provided from the abutting portions 302 r and 302 l whilerecessed by t in the width direction from the abutting portions 302 rand 302 l.

The regulating portions 322 r and 322 l are continuously provided forthe purpose of backup in the case of the thin sheet having the basisweight of about 50 g. The recess width t of each of the regulatingportions 322 r and 322 l is set such that the abutting portions are incontact with the sheet S even if the side regulating plates 32 r and 32l are most inclined on a manufacturing tolerance. In other words,projection amounts of the abutting portions 302 r and 302 l are set suchthat the abutting portions 302 r and 302 l abut on the side edges of thesheet S even if the regulating portions 322 r and 322 l are mostinclined with respect to the sheet feeding direction. In the secondembodiment, the recess width t is set to 5 mm. Similarly to the firstembodiment, the abutting portions 302 r and 302 l are provided oppositeeach other as illustrated in FIG. 8C.

A positioning operation of the sheet S, which is performed by the sideregulating plates 32 r and 32 l having the above-describedconfiguration, will be described below. FIG. 9A illustrates a state inwhich a thin sheet S′ is positioned by the side regulating plates 32 rand 32 l having maximum inclinations θ1 on the manufacturing tolerance.FIG. 9B illustrates a state immediately after the thin sheet S′ is fedby the sheet feeding roller 3 c while the difference between the rightand left diameters of the thin sheet S′, the balance between the rightand left diameters, and the alignment with respect to the sheet feedingdirection are not adjusted.

The lengths δ and the widths t of the abutting portions 302 r and 302 lare set to the above-described values in positioning the thin sheet S′,whereby the abutting portions 302 r and 302 l abut on the side edges ofthe thin sheet S′ at the substantially same position as illustrated inFIG. 9A similarly to the first embodiment. Part of the regulatingportion 322 r also abuts on the thin sheet S′.

At this point, it is assumed that a force F7 is applied to the thinsheet S′ during a process in which the thin sheet S′ is fed by the sheetfeeding roller 3 c. When the side edges of the thin sheet S′ areregulated by the abutting portions 302 r and 302 l having the lengths δ,the force acting on the side edge per unit length of the thin sheet S′is increased with decreasing length δ. As a result, sometimes the sideedges of the thin sheet S abutting on the abutting portions 302 r and302 l are deformed to hardly regulate the rotation of the thin sheet S′depending on the settings of the lengths 6 of the abutting portions 302r and 302 l or a kind of the thin sheet S′. In such cases, the thinsheet S′ rotates.

On the other hand, in the second embodiment, the side edges of the thinsheet S′ are regulated by the backup regulating portions 322 r and 322 lprovided on the upstream side in the sheet feeding direction of theabutting portions 302 r and 302 l as illustrated in FIG. 9B, so that theexcess skew feeding can be prevented. Thus, in the second embodiment,the excess skew feeding can be prevented by providing the backupregulating portions 322 r and 322 l even if the thin sheet S′ is fed.

A third embodiment of the invention will be described below. FIGS. 10Aand 10B illustrate a configuration of a movable portion of the sideregulating plates provided in the sheet tray 3 a of a sheet feedingapparatus of the third embodiment. In FIGS. 10A and 10B, the same orequivalent component is designated by the same numeral as that of FIG.3.

In FIG. 10A, a fixing portion 11 r is provided on the side regulatingplate guide 32 (see FIG. 3) to fix side regulating plates 33 r and 33 l,and a rack-shaped tooth is provided in the fixing portion 11 r. Alatching portion 10 r is provided in a rack member 7 r of the sideregulating plate 33 r, and a projection which elastically engages withthe fixing portion 11 r is provided in the latching portion 10 r.

When the side regulating plates 33 r and 33 l are moved in the directionin which the side regulating plates 33 r and 33 l come close to eachother, the latching portion 10 r of the side regulating plate 33 r ispressed against the rack-shaped tooth of the fixing portion 11 r, andthe latching portion 10 r is subjected to a force in a bending directionby the rack-shaped tooth, whereby the latching portion 10 r is movedbeyond the rack-shaped tooth. Therefore, the side regulating plates 33 rand 33 l can be moved in the direction in which the side regulatingplates 33 r and 33 l come close to each other.

On the other hand, when the side regulating plates 33 r and 33 l aremoved in the direction in which the side regulating plates 33 r and 33 lare separated from each other, the side regulating plates 33 r and 33 lcannot be moved because the latching portion 10 r of the side regulatingplate 33 r is latched in the rack-shaped tooth of the fixing portion 11r. As illustrated in FIG. 11B, when the side regulating plates 33 r and33 l are moved in the direction in which the side regulating plates 33 rand 33 l are separated from each other, a lever 12 r provided in thelatching portion 10 r is pressed in a direction of an arrow C by afinger to elastically bend the latching portion 10 r. Therefore, thelatching of the latching portion 10 r in the rack-shaped tooth of thefixing portion 11 r is released.

When the fixing portion 11 r is provided, the positioning isstrengthened in the direction in which the side regulating plates 33 rand 33 l are opened, namely, the direction in which the side regulatingplates 33 r and 33 l are separated from each other. On the other hand,as illustrated in FIG. 10B, the movement in the direction in which theside regulating plates 33 r and 33 l are closed, namely, the directionin which the side regulating plates 33 r and 33 l come close to eachother can be performed on a pitch p of the rack-shaped tooth of thefixing portion 11 r.

Therefore, as illustrated in FIG. 11, one of the sheet regulatingportions 303 r and 303 l is elastically formed so as to abut on the sideedge of the sheet S even if the side regulating plates 33 r and 33 l areopened by the pitch p. In the third embodiment, the sheet regulatingportion 303 r is elastically formed. The sheet regulating portion 303 lis provided across the sheet S from the elastically-formed sheetregulating portion 303 r.

As a result, because the sheet regulating portions 303 r and 303 l abuton the side edges of the sheet S even if the side regulating plates 33 rand 33 l are opened by the pitch p of the rack-shaped tooth, the effectsimilar to that of the second embodiment can be obtained. As describedabove, in the configuration of the third embodiment in which themovements in the width directions of the side regulating plates 33 r and33 l are positioned by the rack-shaped tooth, the inexpensive sheetfeeding apparatus advantageous to the skew feeding can be provided bythe simple configuration.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2010-173729, filed Aug. 2, 2010, which is hereby incorporated byreference herein in its entirety.

1. A sheet feeding apparatus comprising: a sheet storage portion whichstores sheets; a sheet feeding roller which feeds the sheet stored inthe sheet storage portion; a pair of side edge regulating portions whichis provided opposite each other in the sheet storage portion so as toregulate positions of side edges in a width direction orthogonal to asheet feeding direction of the stored sheet, and at least one of thepair of side edge regulating portions can be moved in the widthdirection; and projection portions provided opposite each other on innerwall surfaces of the side edge regulating portions so as to abut on theside edges of the sheet, respectively.
 2. The sheet feeding apparatusaccording to claim 1, wherein a projection amount of the projectionportion is set such that the projection portion abuts on each side edgeof the sheet even if the pair of side edge regulating portions is mostinclined with respect to the sheet feeding direction.
 3. The sheetfeeding apparatus according to claim 1, wherein a length of theprojection portion of the side edge regulating portion is set to a rangeof 0.5 (mm)≦X′≦30 (mm).
 4. The sheet feeding apparatus according toclaim 1, comprising a sheet conveying portion which conveys the sheetfed by the sheet feeding roller while nipping the sheet, wherein theprojection portion is provided at a position at which the projectionportion abuts on each side edge of the sheet until the sheet reaches thesheet conveying portion.
 5. The sheet feeding apparatus according toclaim 4, wherein the plurality of sheet conveying portions is providedin the width direction.
 6. The sheet feeding apparatus according toclaim 1, wherein a regulating portion is provided on the inner wallsurface of the side edge regulating portion and on an upstream side inthe sheet feeding direction of the projection portion, the regulatingportion abutting on the sheet to regulate inclination of the sheet whenthe sheet is bent by abutting on the projection portion.
 7. The sheetfeeding apparatus according to claim 1, wherein at least one of the pairof side edge regulating portions is configured to elastically abut onthe side edge of the sheet.
 8. An image forming apparatus comprising: asheet feeding apparatus in which a sheet stored in a sheet storageportion is fed by a sheet feeding roller; an image forming portion whichforms an image in the sheet fed by the sheet feeding apparatus; and apair of side edge regulating portions which is provided opposite eachother in the sheet storage portion so as to regulate positions of sideedges in a width direction orthogonal to a sheet feeding direction ofthe stored sheet, wherein at least one of the pair of side edgeregulating portions can be moved in the width direction, and projectionportions are provided opposite each other on inner wall surfaces of theside edge regulating portions so as to abut on the side edges of thesheet, respectively.
 9. The image forming apparatus according to claim8, wherein a projection amount of the projection portion is set suchthat the projection portion abuts on the side edges of the sheet even ifthe pair of side edge regulating portions is most inclined with respectto the sheet feeding direction.
 10. The image forming apparatusaccording to claim 8, wherein a length of the projection portion of theside edge regulating portion is set to a range of 0.5 (mm)≦X′≦30 (mm).11. The image forming apparatus according to claim 8, comprising a sheetconveying portion which conveys the sheet fed by the sheet feedingroller while nipping the sheet, wherein the projection portion isprovided at a position at which the projection portion abuts on eachside edge of the sheet until the sheet reaches the sheet conveyingportion.
 12. The image forming apparatus according to claim 11, whereinthe plurality of sheet conveying portions is provided in the widthdirection.
 13. The image forming apparatus according to claim 8, whereina regulating portion is provided on the inner wall surface of the sideedge regulating portion and on an upstream side in the sheet feedingdirection of the projection portion, the regulating portion abutting onthe sheet to regulate inclination of the sheet when the sheet is bent byabutting on the projection portion.
 14. The image forming apparatusaccording to claim 8, wherein at least one of the pair of side edgeregulating portions is configured to elastically abut on the side edgeof the sheet.